1. Field of the Invention
The present invention relates to a switch, a network system and a traffic movement method, and more particularly to a switch, a network system and a traffic movement method for use in a layer 2 network having a layer 2 switch.
2. Description of the Related Art
In a layer 2 network configured using a layer 2 switch, it may be desired in some cases to change lines in a certain section because of a line trouble, deterioration or speed-up. In this case, for the reason that the line is already active, it is desired to change this line without lacking communication in the currently flowing traffic.
In such a case, as a first technique there is a method for changing the lines using a link aggregation as defined in the IEEE802.3ad. Herein, the line in current use is called an old line, and the line after changing is called a new line. There is another method that once a configuration of link aggregation is built of the new line and the old line, the traffic is moved from the old line to the new line by blocking the old line or using a function of the link aggregation.
Reference to FIGS. 1, 2 and 3 is made for explanation. Herein, FIG. 1 shows a layer 2 network (100) configured using a layer 2 switch. FIG. 2 is a diagram showing in excerpt a layer 2 switch 1 (201), a layer 2 switch 2 (202), and four terminals as exemplified in the layer 2 network (100). Herein, the case of changing a line 1 (401) is considered. A line 6 (406) is connected as the new line, and the configuration is built with the line 1 (401) and the line 6 (406) as the link aggregation, as shown in FIG. 3. Thereafter, the line 1 (401) is blocked, and the traffic via the line 1 (401) is moved via the line 6 (406) using the link aggregation function.
A second technique not using the link aggregation is a method that two lines of the old line and the new line are temporarily connected between the apparatuses, and the traffic is moved from the old line to the new line by clearing an FDB (also called Forwarding Data Base, Filtering Data Base).
Reference to FIGS. 2, 4 and 5 is made for explanation. Herein, FIG. 2 has been already described above. FIGS. 4A to 4C are diagrams in which the line 6 (406) of the new line is connected in FIG. 2, and a traffic flow is additionally written in accordance with a procedure based on this line 6. FIG. 4A is a diagram in which the line 6 (406) of the new line to be changed from the line 1 (401) is connected from a state of FIG. 2. FIG. 4B shows the traffic flow before changing. In the figure, arrows (501) and (502) indicate the traffic flows. FIG. 4C shows traffic flows (503) to (506) after clearing the FDB in the layer 2 switch 1 (201). FIGS. 5A to 5C show an FDB (601) of the layer 2 switch 1 (201) and an FDB (604) of the layer 2 switch 2 (202) at the timing of each of FIGS. 4A to 4C. In each figure, E1 to E4 designate the entries of FDB.
Before clearing the FDB, the traffic flows (501) and (502) are via the line 1 (401), as shown in FIG. 4B. This is because the traffic is transferred in accordance with an FDB (601-2) and an FDB (604-2) as shown in FIG. 5B. Herein, an entry regarding the line 1 (401) of the layer 2 switch 1 (201) is cleared from the FDB (601-2). In this case, the entry (E3) and the entry (E4) apply and are cleared.
At this point of time, the traffic originated from a terminal 11 (301) and directed to a terminal 21 (303) in the traffic (501) and the traffic originated from a terminal 12 (302) and directed to a terminal 22 (304) in the traffic (502) become flooding. Because of flooding, the traffic also flows via the line 6 (406), and the traffic moves by way of the line 6 (406). In the layer 2 switch 2 (202), if the FDB is similarly cleared, the traffic originated from the terminal 21 (303) and the terminal 22 (304) and directed to the terminal 11 (301) and the terminal 12 (302) can be also moved.
At the point of time when the FDB is deleted, the communication is made by flooding. Therefore, the traffic flows to the line 6 (406), and at the same time the traffic is sent out to the line 1 (401). In this regard, if another means such as filtering is employed, it is possible to stop sending out the traffic to the line 1 (401).
Also, there was disclosed a technique for changing the port of output destination by providing a transfer switching table in addition to the FDB (e.g., refer to JP-A-2007-181049). For example, besides the FDB, a table for managing sending line information is provided to store a plurality of pieces of line information to be switched.